MDCAT/ECAT Chemistry Quiz # 1 🧬 | Representative Elements High-Yield Chemistry MCQs💥 Exam-Focused, 🎯 💯 Exam Booster🚀 Practice & Win 190+! 📚 Topper’s Choice

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MDCAT/ECAT Quiz # 1 (Group Trend of Representative Elements): InamJazbi Learn Chemistry 🚀

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1. Melting and boiling points of which of the following group of representative elements decrease regularly down the group?

• ☐ a) Group IA
• ☐ b) Group IIIA
• ☐ c) Group VIIA
• ☐ d) Group VIIIA

Show Answer & Explanation

✅ Answer: a) Group IA
Explanation: Metallic bonds weaken as atomic size increases, so melting & boiling points decrease down the group.

2. Which of the following s-block elements forms superoxide when burned in air?

• ☐ a) Li
• ☐ b) Na
• ☐ c) K
• ☐ d) Mg

Show Answer & Explanation

✅ Answer: c) K
Explanation: Superoxides contain O₂⁻. Larger alkali metals like K, Rb, Cs form superoxides because their large cations stabilize the O₂⁻ ion. Li forms normal oxide, Na forms peroxide, Mg forms normal oxide.

3. Which of the following formula of nitrides for alkaline earth metal is possible?

• ☐ a) MN₃
• ☐ b) M₂N₃
• ☐ c) M₃N
• ☐ d) M₃N₂

Show Answer & Explanation

✅ Answer: d) M3N2
Explanation: Alkaline earth metals have +2 charge (M²⁺), nitride ion is N³⁻. LCM of 2 and 3 = 6 → formula = M3N2.

4. The flame colour of which of the following alkali metals is yellow?

• ☐ a) Na
• ☐ b) K
• ☐ c) Rb
• ☐ d) Cs

Show Answer & Explanation

✅ Answer: a) Na
Explanation: Flame test colors: Li → crimson red, Na → bright yellow, K → lilac, Rb → red-violet, Cs → blue-violet.

5. The chemical used in fireworks is:

• ☐ a) Bleaching powder
• ☐ b) Sodium bicarbonate
• ☐ c) Potassium nitrate
• ☐ d) Potash alum

Show Answer & Explanation

✅ Answer: c) Potassium nitrate
Explanation: KNO₃ is a strong oxidizer needed for rapid combustion and colorful explosions. Others are not suitable.

6. Cathode in Castner Kellner cell is:

• ☐ a) Titanium blocks
• ☐ b) Carbon rods
• ☐ c) Mercury
• ☐ d) Iron container

Show Answer & Explanation

✅ Answer: c) Mercury
Explanation: Cathode is mercury (Hg), anode is titanium.

7. The diagonal member of beryllium is:

• ☐ a) Mg
• ☐ b) Al
• ☐ c) Si
• ☐ d) C

Show Answer & Explanation

✅ Answer: b) Al
Explanation: Be and Al have a diagonal relationship due to similar charge/radius ratio and electronegativity.

8. Purification of SO₂ from arsenic oxide is essential in the contact process to avoid:

• ☐ a) Catalyst poisoning
• ☐ b) Temperature elevation
• ☐ c) Pressure controlling
• ☐ d) Air mixing

Show Answer & Explanation

✅ Answer: a) Catalyst poisoning
Explanation: Arsenic oxide poisons the V₂O₅ catalyst in the SO₂ → SO₃ reaction, reducing efficiency.

9. Oil of vitriol refers to:

• ☐ a) Borax
• ☐ b) Sulphuric Acid
• ☐ c) Alum
• ☐ d) Caustic soda

Show Answer & Explanation

✅ Answer: b) Sulphuric Acid
Explanation: “Oil of vitriol” is the old alchemical name for H₂SO₄ due to its oily appearance.

10. The best oxidizing agent among halogens is:

• ☐ a) F₂
• ☐ b) Cl₂
• ☐ c) Br₂
• ☐ d) I₂

Show Answer & Explanation

✅ Answer: a) F₂
Explanation: Fluorine has the highest reduction potential (+2.87 V) and electronegativity, making it the strongest oxidizer among halogens. Oxidizing power decreases down the group: F₂ > Cl₂ > Br₂ > I₂.

11. The electronic configuration of s-block metal, M is 1s² 2s² 2p⁶ 3s¹. The formula of its oxide would be:

• ☐ a) MO
• ☐ b) M₂O
• ☐ c) M₂O₂
• ☐ d) MO₂

Show Answer & Explanation

✅ Answer: b) M₂O
Explanation: M has configuration 1s² 2s² 2p⁶ 3s¹ → Group IA (Na). Oxidation state = +1, O²⁻. Balance charges: 2M⁺ + O²⁻ → M₂O.

12. The element lithium bears resemblance with:

• ☐ a) Al
• ☐ b) Mg
• ☐ c) Si
• ☐ d) None of them

Show Answer & Explanation

✅ Answer: b) Mg
Explanation: Lithium (Li) shows diagonal relationship with Mg: similar ionic sizes, charge/radius ratio. Both form nitrides (Li₃N, Mg₃N₂), sparingly soluble salts, and show covalent character in many compounds.

13. The electronic configuration of a metal, M is 1s² 2s². The diagonal member of this element has electronic configuration:

• ☐ a) 1s² 2s¹
• ☐ b) 1s² 2s² 2p⁶ 3s¹
• ☐ c) 1s² 2s² 2p⁶ 3s² 3p¹
• ☐ d) 1s²

Show Answer & Explanation

✅ Answer: c) 1s² 2s² 2p⁶ 3s² 3p¹
Explanation: M = Be (1s² 2s²). Diagonal relationship: Be ↔ Al. Al configuration = 1s² 2s² 2p⁶ 3s² 3p¹.

14. Which of the following s-block elements only forms normal oxide when burned in air?

• ☐ a) Li
• ☐ b) Be
• ☐ c) Mg
• ☐ d) All of them

Show Answer & Explanation

✅ Answer: d) All of them
Explanation: Li → Li₂O, Be → BeO, Mg → MgO. All form only normal oxides.

15. Which of the following alkali metals only forms normal oxide when burned in air?

• ☐ a) Li
• ☐ b) Be
• ☐ c) Ca
• ☐ d) Na

Show Answer & Explanation

✅ Answer: a) Li
Explanation: Only Li forms normal oxide (Li₂O). Na forms peroxide, K/Rb/Cs form superoxides.

16. Which of the following formula of nitrides for alkali metal is possible?

• ☐ a) MN₃
• ☐ b) M₂N₃
• ☐ c) M₃N
• ☐ d) MN

Show Answer & Explanation

✅ Answer: c) M₃N
Explanation: Alkali metals = +1, N³⁻ → 3M⁺ + N³⁻ → M₃N. Only lithium forms stable nitride (Li₃N) at room temperature.

17. Which of the following formula of nitrides for Group IIIA is possible?

• ☐ a) MN₃
• ☐ b) M₂N₃
• ☐ c) M₃N
• ☐ d) MN

Show Answer & Explanation

✅ Answer: d) MN
Explanation: Group IIIA = +3, N³⁻ → charges balanced 1:1 → MN.

18. Which group elements form nitrides with general formula M₃N₄?

• ☐ a) IIIA
• ☐ b) IIA
• ☐ c) VA
• ☐ d) IVA

Show Answer & Explanation

✅ Answer: d) IVA
Explanation: Group IVA = +4, N³⁻ → 3(M⁴⁺) + 4(N³⁻) → M₃N₄.

19. Which group elements form nitrides with general formula M₃N₅?

• ☐ a) IIIA
• ☐ b) IVA
• ☐ c) VA
• ☐ d) IIA

Show Answer & Explanation

✅ Answer: c) VA
Explanation: Group VA = +5, N³⁻ → 3(M⁵⁺) + 5(N³⁻) → M₃N₅.

20. Which group elements form superoxides with general formula MO₂?

• ☐ a) IA
• ☐ b) IVA
• ☐ c) IIIA
• ☐ d) IIA

Show Answer & Explanation

✅ Answer: a) IA
Explanation: Larger alkali metals (K, Rb, Cs) stabilize O₂²⁻ → form MO₂ superoxides.

21. Which of the following gas is evolved when phosphorus reacts with water?

• ☐ a) NH₃
• ☐ b) PH₃
• ☐ c) H₂
• ☐ d) H₂S

Show Answer & Explanation

✅ Answer: b) PH₃
Explanation: White phosphorus reacts with hot concentrated alkali or under special conditions to produce phosphine (PH₃). This is an auto-redox reaction: P oxidized to phosphoric acid (P⁵⁺) and reduced to PH₃ (P³⁻). With pure water the reaction is negligible.

22. The general formula of alkali metal alkoxide is:

• ☐ a) C₂H₅OM
• ☐ b) C₂H₅COONa
• ☐ c) (C₂H₅)₂M
• ☐ d) None of them

Show Answer & Explanation

✅ Answer: a) C₂H₅OM
Explanation: Alkali metals (M⁺) react with alkoxide ion (RO⁻, e.g., C₂H₅O⁻) → M⁺ + RO⁻ → C₂H₅OM.

23. The chemical formula of lithium ethoxide is:

• ☐ a) (C₂H₅)₂Li
• ☐ b) C₂H₅COOLi
• ☐ c) C₂H₅OLi
• ☐ d) None of them

Show Answer & Explanation

✅ Answer: c) C₂H₅OLi
Explanation: Lithium ion (Li⁺) reacts with ethoxide (C₂H₅O⁻) → C₂H₅OLi or LiOC₂H₅.

24. Alkali metals react with alcohols liberating hydrogen gas along with:

• ☐ a) Alkoxide
• ☐ b) Phenoxide
• ☐ c) Carboxylate
• ☐ d) None of them

Show Answer & Explanation

✅ Answer: a) Alkoxide
Explanation: 2M + 2C₂H₅OH → 2C₂H₅OM + H₂↑ [M = Li, Na, K]. Alkali metals displace hydrogen from alcohol, forming alkoxide salts and H₂ gas.

25. The Group IA elements react violently with water making the solution:

• ☐ a) Acidic
• ☐ b) Neutral
• ☐ c) Alkaline
• ☐ d) Amphoteric

Show Answer & Explanation

✅ Answer: c) Alkaline
Explanation: 2M + 2H₂O → 2MOH + H₂↑. Alkali metal hydroxides (MOH) are strong bases → solution becomes alkaline.

26. Which of the following alkali metals imparts lilac colour to the flame?

• ☐ a) K
• ☐ b) Li
• ☐ c) Cs
• ☐ d) Na

Show Answer & Explanation

✅ Answer: a) K
Explanation: Flame test colors: Li → crimson red, Na → bright yellow, K → lilac, Rb → red-violet, Cs → blue-violet.

27. Which of the following metals floats over water?

• ☐ a) Cs
• ☐ b) Na
• ☐ c) Rb
• ☐ d) Be

Show Answer & Explanation

✅ Answer: b) Na
Explanation: Density < 1 g/cm³ → floats. Na = 0.97 g/cm³, Li = 0.53 g/cm³, K = 0.86 g/cm³ → float; Cs, Rb, Be → sink.

28. The basic strength of alkaline earth metals oxides in water _____ from Be to Ba.

• ☐ a) Decreases
• ☐ b) Increases
• ☐ c) Remains same
• ☐ d) Not predictable

Show Answer & Explanation

✅ Answer: b) Increases
Explanation: MO + H₂O → M(OH)₂. Solubility and ionic character increase down the group → basic strength ↑ (Be → Ba).

29. The element cesium bears resemblance with:

• ☐ a) Cr
• ☐ b) Ca
• ☐ c) Both a and b
• ☐ d) None of them

Show Answer & Explanation

✅ Answer: d) None of them
Explanation: Cs is an alkali metal in Group I; no diagonal relationship exists with Cr or Ca → does not resemble.

30. Which of the following sulphates is NOT soluble in water?

• ☐ a) BaSO₄
• ☐ b) ZnSO₄
• ☐ c) K₂SO₄
• ☐ d) Na₂SO₄

Show Answer & Explanation

✅ Answer: a) BaSO₄
Explanation: Most sulfates soluble except Ba²⁺, Pb²⁺, Sr²⁺, Ca²⁺ (slightly). BaSO₄ → insoluble; others soluble.